Re: Clock or anemometer?

Andrew Nahum

I should introduce myself as a newcomer here. I have a fairly long term interest in synchronomes - though not as long as you guys - and I see that I bought my first one over twenty years ago since when it has run pretty perfectly as the house clock in our main room, subject to periodic cleaning and adjustment. I have often wondered what the limits are of the clock and what the sources of error are. In a way, it should be better.  But I have not tried optical sensing and better impulsing and love to hear what this group is doing. I also run a Brillie in the same room and my one, anyway, is definitely less stable than the Synchronome. 

Bepi - I asked about where the barometric data came from because I had thought the local aerodynamic effects of wind on the building could cause a divergence inside the house which might last for a considerable period. ie. that the effects you see were a secondary effect of wind speed and perhaps not driven by wind speed per se.  I wasn’t thinking about waves, so much as a relatively continuous pressure change of either sign away from the external barometric pressure that could last for hours or maybe a day. But I gather now that you are fully instrumented for pressure at the clock itself, so my speculation would not be valid. A

On 4 Apr 2020, at 22:41, Bepi <pepicima@...> wrote:

Turbulence is certainly very broad band and the pendulum is sampling at 1/2 Hz, what I see is down to the sampling frequency and its SD looks like the wind speed, most of its power is up there, frequency wise,  where we see it by eye. Yes the 3 baro sensors I have in the case are fast enough, they are essentially low frequency microphones. I could cross correlate them to analyze a broad spectrum with exceptional sensitivity, but luckily they have been off for some time now, they were not yielding anything more useful than the city barometer which is more reliably calibrated. These days it's far less windy, I was hoping nobody would have suggested that measurement. I totally agree about the spectrum, its knowledge is essential to see if these fluctuations matter for standard long term accuracy but wouldn't be easier to check if accuracy correlates with windy days? Something else to keep in mind when checking for regular, long term, atmospheric pressure correlations. John, weren't you working on this already?

Chris, thanks for all that fun info on infrasonics but at the end of the day, if I could put my apartment under high vacuum, would I still see those fluctuations or not?

Andrew why you ask about depressurization? Pressure waves or vibrations aren't they all zero average waves?


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